Most computers use disk drives to store data. A disk drive typically includes one or more disks that the data is stored on, and read write heads that are used to write data onto the disks and to read the data from the disks. The read write head is built on a substrate which is then machined so that it has aerodynamic properties which allows the slider to “fly” over a disk. A slider flies over a location on a disk for the purpose of writing data to that location or reading data from that location.
FIG. 1 depicts a side view of a conventional slider. The slider 100 includes a write head 108 for writing data to a disk and a read sensor 106 for reading data from a disk. The read sensor 106 has a height, which is commonly known as a stripe-height 102. The air bearing surface 104 (ABS) of the slider 100 provides the aerodynamic properties that enables the slider 100 to “fly” over a disk.
In order for the slider 100 as well as the read sensor 106 and the write head 108 to function properly, the ABS 104 needs to be very flat and smooth and the read sensors 106 need to have an appropriate stripe-height 102. A lapping plate is used for grinding and/or polishing the ABS 104 (commonly referred to as the “lapping process”) in order to achieve the desired smoothness and the desired stripe-height 102. A lapping plate typically has abrasive particles, such as diamond particles, on its surface that can be used to remove material from the slider 100 and/or to polish the slider 100.
The particles are typically embedded into the lapping plate surface using what is commonly known as a “charging process.” Lapping plates are manufactured by placing slurry, which contains particles such as diamond particles of known size, on the lapping plate. The particles are embedded into the lapping plate using the charging process, as will become more evident.
To date, much of the industry has typically used water based slurries. However, the industry is moving toward oil-based slurries. Oil-based slurries are commonly known by the industry to have problems. For example, it is important that the particles be suspended in the slurry. However, the particles in the oil-based slurries are known to clump together (also commonly known as “agglomeration”). The agglomeration of the particles can result, among other things, in lapping plates having defects. Scratches, clumps of particles embedded into the lapping plate, and areas of the lapping plate with no embedded particles are examples of “defects.” A lapping plate of inferior quality will damage sliders 100 and therefore cannot be used to lap sliders 100.
Tests have been performed on conventional lapping plates manufactured with oil-based slurries using conventional techniques to assess the quality of the lapping plates. The conventional lapping plates with five inch diameters were inspected visually using 100× magnification. The defects were counted along the respective diameters of numerous five inch conventional lapping plates. It was found that on the average the conventional lapping plates had greater than 200 defects. It was also determined that lapping plates with 100 defects or fewer were of a sufficient quality to lap sliders 100.